A coil assembly such as a transformer includes a bobbin and coils or conductive wires wound over the bobbin. The bobbin has generally cylindrical shape, and a plurality of wires each coated with an electrically insulation layer are wound over an outer peripheral surface of the bobbin. Each wire has a winding portion wound over the bobbin and draw-out portions at each end portion of the wire.
Japanese Patent Application Publication No. H08-111323 discloses a coil assembly in which a terminal base is provided at one axially end portion of a cylindrical portion. The terminal base is provided with a plurality of pin terminals protruding in a direction perpendicular to a circuit board when the coil assembly is surface-mounted on the board. The terminal base is provided with an engaging portion protruding outward so as to engage the draw-out portion of the wire and to direct the draw-out portion toward the pin terminal. Each end portion of the wire is wound over the pin terminal and is electrically connected thereto.